Single- versus multiple-sample method to measure glomerular filtration rate.

Area of Science:

• Nephrology
• Pharmacokinetics
• Clinical Chemistry

Background:

• Glomerular filtration rate (GFR) measurement utilizes various exogenous markers with differing strengths and limitations.
• Methodologies for GFR assessment, including urinary or plasma clearance and the number of time points for area under the concentration-time curve calculation, exhibit significant variability.

Purpose of the Study:

• To evaluate the accuracy of the single-sample GFR estimation method (Jacobsson formula) against a multiple-sample clearance strategy.
• To determine the optimal time point for single-sample GFR measurement using plasma clearance.

Main Methods:

• Analysis of 5106 plasma clearances using iohexol or 51Cr-EDTA with three to four time points.
• GFR calculation via slope-intercept method with Bröchner-Mortensen correction.
• Application of the Jacobsson formula for single-sample GFR at each time point and comparison using Bland-Altman plots.

Main Results:

• Single-sample GFR concordance with multiple-sample GFR was 66.4% (120 min), 83.6% (180 min), 91.4% (240 min), and 96.0% (≥300 min) within 10% agreement.
• Concordance was reduced in individuals with lower GFR levels (<30 mL/min), increasing age, and in obese subjects.
• Results were consistent between males and females.

Conclusions:

• The single-sample GFR method demonstrates high concordance with multiple-sample strategies, particularly at later time points (≥300 min).
• Accuracy of the single-sample method is compromised in the low GFR range (<30 mL/min).